Crossword Genius

Idiotic square like one before (7)

Ross

I believe the answer is:

asinine

'idiotic' is the definition.
(thesaurus)

'square like one before' is the wordplay.
'square' becomes 'nine' (I've seen this before**).
'like' becomes 'as'.
'one' becomes 'i' (Roman numeral).
'before' is a charade indicator (letters next to each other).
'as'+'i'='asi'
'nine' after 'asi' is 'ASININE'.

(Other definitions for asinine that I've seen before include "Daft" , "Stupid (as a donkey?)" , "Foolish, silly" , "'Mindless, vacuous (7)'" , "Silly like a donkey" .)

I've seen this clue in The Guardian.
Want a hint initially instead of a full solution? Install my app